FLOW CYTOMETRY SHARED RESOURCE PROJECT SUMMARY/ABSTRACT Flow Cytometry Shared Resource was established in 2004 to provide ready and affordable access to state-of- the-art multi-parameter cell analysis and sorting capabilities. This facility is comprised of a large number and variety of flow cytometry instruments that quantify the fluorescence of individual cells, typically following staining with specific antibodies. Flow cytometry has become an important tool in cancer research for many different purposes. Some important applications include the immune profiling of tumor microenvironment and the phenotyping of cancer cells. Cell sorting by Flow Cytometry is critical for the purification of cells for genomics, proteomics, metabolomics, or the isolation of tumor stem cells. This institutional resource serves the entire Yale School of Medicine (YSM) campus, including Yale Cancer Center (YCC), and thus has a critical mass of users supporting these large and expensive instruments. During the most recent funding period, 197 laboratories have used Flow Cytometry. Ninety-four of these users (48%) were YCC members. This Shared Resource was most widely used by the Genomics, Genetics and Epigenetics (GGE) and the Cancer Immunology (CI) Research Programs. A wide variety of assays are performed, and the laboratory also offers consulting on experimental protocols with its experienced full-time director. Flow cytometry has multiple applications in cancer research. For example, as the pace of research into cancer immunology and biologic therapies increases, defining the functional and phenotypic heterogeneity of mixed cell populations will continue to be a critical technology in cancer research. Flow cytometry is not only essential for cancer immunology research, but also empowers numerous other types of studies such as oncogenesis, cell signaling events, preclinical models, the assessment of therapeutic efficacy, gene editing using CRISPR and of course, cell sorting for genomic and RNA sequencing. Clearly, Flow Cytometry is vital to a number of programs within YCC. The Specific Aims of Flow Cytometry are to: (1) Provide flow cytometry services that are of high quality, readily available, and at reasonable cost; (2) Educate the YCC community on the applications of flow cytometry in medical research; and (3) Collaborate with YCC investigators in the development of new applications.